Please, do not attempt if you don\'t have a good understanding of the questions.
ID: 3308856 • Letter: P
Question
Please, do not attempt if you don't have a good understanding of the questions. Look for questions you thoroughly understand. Thank you.
Kindly provide textbook references.
State whether the following processes are possible or impossible and (a) A single photon strikes a stationary electron and gives up all its b) A single photon in empty space is transformed into an electron and (c) A fast positron and a stationary electron annihilate, producing only prove your statement: energy to the electron. a positron. one photon.Explanation / Answer
(a) This process is not possible
The given process is photon + electron -> electron'
Initial invariant mass is, (Eph + me)² - pph² = 2Eph me + me² ---(since photon is massless Eph² - pph² = 0)
Final invariant mass of the resulting electron is Eel'² - pel'² = me²
Equating the two, we end up with 2Eph me = 0
However neither photon energy is zero nor mass of electron is zero
(b) This process is also not possible due to the same reasoning as in (a)
Photon invariant mass is zero
electron and positron combined invariant mass is (Eel + Epos)² - (pel + ppos)²
Resulting in me² + mpos² - pel . ppos ---(momentum is a vector, we need to take dot product)
Mass of electron = mass of positron. So the final expression becomes
2me² - pel . ppos
which is greater than zero.
(c) This process is the inverse of (b). The final expression of (b) is initial invariant non-zero invariant mass. And the resulting photon is zero invariant mass.
And due to same reasoning, it is not possible as well
(d) Proved in (b).